They are all reloads. Thai is a single bolt action upper also.
Single loading with standing...if it was shot in a 50 BMG and it was a little out of time or hrad space...or both.....the case is toooo long.
Measure the cases to be sure you are not sticking them in the leade.
Delta6, please tell me more. I do not no anything about headspaceing or timeing.
If I can chamber the round unfired and extract it unfired with no issue would the case be stretching after fired?
I will measure some empty brass full lenght and some unfired brass and see if their is a difference.
To keep it simple (quick version), timing and headspace (and at times a worn chamber) can regulate whether a 50 BMG will not fire, as to not have a stoppage, change rate of fire or blow itself up. The timing can be off a bit as can the headspace and the gun will still function. When the timing or the headspace or both are out of operational parameters and the gun is still functioning, it is possible that case stretching, case separation and/or neck stretching will occur, yes even on the first firing.
So, how does this relate to your problem. If your cases (case OAL, not cartridge OAL) are too long, some of your case may actually, upon being chambered, be into the leade or even crowding the end of the barrel. You will still be able to chamber a round and even eject that round as long as it is not fired. Once that round has been fire, since the case is too long to start with, any increase in size will have the possibility to flow the brass into the leade or at this point the barrel, sans a stuck or sticky case to eject.
This may not be your problem, since I have not seen it, but in my experience I have seen this problem many many times and yes, with once fired brass. Once fired means nothing when it comes to 50 caliber, if it was fired in a 50 BMG....once.